Misfire please help (what else could it be)

[Phat VR6 3]

Hello

Ive got my Vr running again after a few years.. first turn of the key BUT its only running on 5 cylinders :@

What ive done so far... Pulled all the leads one buy one and engine drops revs and sounds even more minging apart from when i pull lead 3.. nothing changes

So this been the one that misfiring i swap the leads over with one i know that's working. Still missing on 3. So its not the leads

Next whipped the spark plug out, still looked like new to back up the missfire. swapped with a good one.. still missing on 3, so its not the spark plugs.

Run out and buy a new coilpack. swap still the same so thats going back on Monday.

So as far as im aware thats everything as far as the ignition side of things

So think its fuel... one of the injectors not firing. strip it down, swap 3 for 4 expecting for it to be missing on 4 when i put it back together.

but no still missing on 3

What else can i check for? guess my next job is checking the continuity of the wiring loom see if ive got a snapped wire somewhere fuck cunt fuck fuck

Anyone else got any more ideas

Thanks Tom

[craggsy 91]

You got spark on 3? Have you chaecked wiring along fuel rail?

Whats pressure like on 3?

[Phat VR6 3]

yep got spark, sorry forgot to say. yep the wiring looks fine.. need to check with a multimeter to be sure.

as for fuel pressure to be honest i have know idea how to check single injectors. assumed its the same pressure as the rest as there all off the same rail

[rodney 17]

Well,

you have certainly covered the starters for 10.. so here are some thoughts from outside the box and some obvious ones so sorry dont mean to teach you to suck eggs... and in no particular order

misfire is caused by..

Spark,

Fuel,

mixture,

Electrics/ecu

worth holding the plug against the block. looking for strong spark rather than weak. I cant remember weather 3 is mid-way through the firing order or not. Is timing spot on?

if this has been sat for a while there is an argument for popping a little oil down the plug hole just to lube the world up. If you have any thing in the piston chamber then the oil will help. Turn over with no spark and then clean everything.

The fuel pressure/pump area could mean you are just enough down to miss on one?

How long has the fuel been sat. this may sound daft. but if you have some moisture in there then its a bugger to shift and could cause misfire.

Is it every single beat or some yes some no? If you have the plugs off does it turn over ok or is it hard work with a charged battery?

The fact that the plug is still spotless means there is no carbon discharge. Is it wet? Does it smell of fuel?

Like I say a bit of a ramble but they may spark an idea..

[Phat VR6 3]

is there any other way i can check if im getting fuel though number 3 injector

[craggsy 91]

Well it means taking all injectors out and into jars to check spray pattern and quantity

[rodney 17]

there is a kit. plase see link.. and do the same with jam jars or the likes for the cheap option. Remember to fix in place as the pressure is a couple or 3 bar..

http://www.google.co.uk/products?hl=en&cr=countryUK%7CcountryGB&ei=3Nx9SsmyLuLKjAe3m5HxAQ&resnum=0&q=injector+tester+kit&um=1&ie=UTF-8&ei=6Nx9StncGsafjAeWq-jwAQ&sa=X&oi=product_result_group&ct=title&resnum=5

[Phat VR6 3]

Well' date='

you have certainly covered the starters for 10.. so here are some thoughts from outside the box and some obvious ones so sorry dont mean to teach you to suck eggs... and in no particular order

misfire is caused by..

Spark,

Fuel,

mixture,

Electrics/ecu

worth holding the plug against the block. looking for strong spark rather than weak. I cant remember weather 3 is mid-way through the firing order or not. Is timing spot on?

if this has been sat for a while there is an argument for popping a little oil down the plug hole just to lube the world up. If you have any thing in the piston chamber then the oil will help. Turn over with no spark and then clean everything.

The fuel pressure/pump area could mean you are just enough down to miss on one?

How long has the fuel been sat. this may sound daft. but if you have some moisture in there then its a bugger to shift and could cause misfire.

Is it every single beat or some yes some no? If you have the plugs off does it turn over ok or is it hard work with a charged battery?

The fact that the plug is still spotless means there is no carbon discharge. Is it wet? Does it smell of fuel?

Like I say a bit of a ramble but they may spark an idea..

[/quote']

thanks for the reply . ok ummmm yep £20 of fresh fuel, threads cleaned and lubed. think the pressure is ok as it revs up nicely and it only misses on 3.

Yep constant missing, starts like normal. checked the timing a 100 times lol. only way it could be off is if it jumped. tbf sounds like the timings on.. just missing a cylinder.

As you say ecu/ electrics. its a custom loom so its hidden which means i could have fucked up.. but i was careful

thanks for the info. just them had them sonic cleaned and patten tested before they went in.

really need to get a muitmeter on the injector plug while its running to see if im getting a signal... impossible with the manifold still on :-(

ive been missing the sound of the VR... finally get it back and it sound like this lol

[rodney 17]

have you had it on the VAGCOM?

[Phat VR6 3]

nope the laptops broken.. ive been doing it old skool lol.. vag.com next i think

[spindat45 0]

If all electrical/mechanical checks don't throw up anything conclusive the following might help.

I fitted a s/hand low mileage engine in mine last year. The engine had sat for over a year prior to me purchasing it and wasn't fitted for a futher 9 months. It started first turn of the key with a ZR1 charger fitted but had a missfire below 2000 rpm. It was noticable as you pulled away or blipped the accelerator. It was probably still there over those revs but less noticable. After swapping and checking ALL of the usual suspects, a cylinder leak test confirmed it as having a stuck/sticky valve inlet or exhaust valve, possibly caused by the fact that the engine had sat for some time without being turned over. I tried various cleaners which I added to the tank on a number of occaisions to free up said sticky valve but to no avail. My only option was to port and polish a head with new guides and seals. It's just been fitted and is up and running with a few teething problems but none related to the head or valves (fingers crossed).

Hopefully it's not the same problem for you but worth considering if all else fails. A decent garage should have the relevant equipment to carry out a cylinder leak test. From my own experience, compression tests can prove inconclusive when there is not a drastic difference or loss in compression and often give different readings on the same cylinders. Cylinder leak tests are far more accurate

Hope this helps.

Kevin

[Phat VR6 3]

haahah fuck about geez u tryin to scare me lol

ive done the headgasket lapped the valves seals bla bla and all the rest so im hopping its nothing like that. If the compression is so low to stop it firing id hope a simple compression test would pick that up. something i can do at home. cba with getting it towed to a garage

need my vagcom back but in the mean time i might take craigs advice pull the injector rail out again put them in jam jars and see 3s giving me any fuel

[cabrioman 6]

so have u check the compression on that cylinder ??? and ur 100 % sure u got good spark on that lead .....

[rodney 17]

Is your battery good??? and charging correctly???

[spindat45 0]

haahah fuck about geez u tryin to scare me lol

Not at all. Like I said if all else fails and all the other checks haven't thrown anything up, it might be worth considering. Sounds like you're going through things in the most logical order. As is usually the case, it'll probably turn out to be something simple. . Hope you get it sorted.

[rodney 17]

it'll be the last thing...

[Phat VR6 3]

thanks for the input everyone. RCF your right, my problems are never simple or easy to fix. starting to run out of things on my list now.

tony 100% got spark.. going to leave it for a few days then do a compression test

[cabrioman 6]

ok mate well keep us informed fella

[Phat VR6 3]

well finally checked compression.. compression is good. getting vag.com back tonight

[bungy 2]

Keep us updated, i'm getting frustrated for you. Hope it's something simple and quick to fix.

[djmorgz 0]

i recently had this missfire i tryed everything and it was a wire had pulled out of the loom multiplug and wasnt making a connection.........worth a look tho ...

[Phat VR6 3]

well vag.com just confirmed what i pritty much already new. It didn't magically fix it like i was hopping. Came back with the fault code (No3 injector short to ground)

So thought great. break in the wiring somewhere... got the meter out.

checked from injector plug to big round main plug.. all good.

so then across each side of the plug. all good.

then main plug to ecu plug.. good

Injector plug to ecu plug... good

even from the pin on the outside of the ecu to the circuit board

Found nothing :@.

is there anywhere else i can check for wiring. im just guessing the injector wiring loom goes from the injectors to ECU. can't imagine they go anywhere else.

Only other thing i can think to check is put a new ECU on it? Perhaps the "No3 injector short to ground" code is coming from a dry or dodgy connection inside the ECU?

so to sum up :@ fuck

[cabrioman 6]

try swapping over injectors like number 3 and 4 and see if the code changes could be the injector itself, other than that yeah ecu mate ......

[craggsy 91]

Well like I said before get the injectors out into jars to check spray pattern and quantity to rule out dodgy injector....or swap over 2 injectors

[Phat VR6 3]

ive swapped the injector itself over 3 to 5 and it kept missing on 3. didn't follow the injector. didn't check to see if the code followed it though.

Going to try a different ecu on it. are all obd2 ecus the same or do i need to match the numbers